'Feelings of emptiness' are a criteria for the diagnoses of BPD.
These are definitions from borderlines:
"The void, the hole, something's missing from me that everyone else seems to be in possession of. Something that makes you able to sit and be content. Everything, the emptiness is the lack of being in the moment, getting so anxiously bored in the midst of being unrelentingly busy. Not being here, and not being anywhere else, all at the same time."
"You don't know what it is, but something's missing. Something vital and powerful and profound. You have plans for the future, for yourself, but they mean nothing. They're not even yours; not really. I feel a lack of desire for the future"
"Life's a dream. There's no meaning, no substance, no point. Emptiness is not destructive, it's not without hope, its just a total lack of everything, of motivation, of emotion, of desire. There's no feeling, physically, you're numb."